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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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    <script>
        var n = parseInt(prompt('input a number')), sum = 0;
        for (var i = n ; i >= 2; i--) {
            sum += (i + 1) / i
        }
        alert(sum)
    </script>
</body>
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